The invention relates to a method and apparatus for operating an open-end friction spinning machine having a plurality of spinning units. Each spinning unit includes a friction zone serving as a yarn forming point of region, a feeding and opening device for feeding the fibers to the friction zone, a suction device for holding the fibers and for forming yarn in the friction zone, and a withdrawal device for withdrawing the formed yarn out of the friction zone. The quality of the yarn spun at the spinning units is monitored by means of at least one measuring and evaluating device which triggers an adjusting of at least one parameter of the spinning conditions when there are deviations from the preset desired values of the yarn at the respective spinning unit.
A particular problem with one-end friction spinning is that it has been practically impossible to maintain the yarn quality of the formed yarn over longer periods of time. Differences in the yarn quality at the same spinning unit, as well as fluctuations of quality between yarns of different spinning units have been discovered from time to time. These quality differences are presumably primarily due to fluctuations in friction effect values within the friction zone over a course of time, which changes are difficult to exactly foresee. These fluctuations may be due to wear and tear or to accummulation of dirt particles upon the component parts forming the friction zone. Also, these fluctuations may be due to the characteristics of the fiber material and the spinning environment. For example, the spinning room humidity and temperature level and the amount of grease particles in the fibers being processed may affect the friction effect in the friction zone. In order to alleviate this problem, it has been proposed in accordance with pending commonly owned co-pending patent application Ser. No. 692,972, filed Jan. 22, 1985, to test the quality of the running yarn and upon detection of quality deviations or fluctuations, to accordingly change at least one parameter of the spinning conditions. In accordance with this proposal, a yarn tension sensor is arranged between a withdrawal device and the yarn forming region which monitors the yarn tension of the yarn for purposes of quality control. Conclusions can be drawn from changes in the yarn tension, regarding the quality and, for example, also regarding the applied yarn twist. At least one parameter of the spinning conditions may be changed upon undesirable deviations of the yarn tension in order to again return to the desired normal condition. This sort of indirect quality control of the formed yarn is easily realized and will also be sufficient in many instances. However, the danger does exist that this sort of quality control will no longer be sufficient under extreme circumstances, especially with high yarn withdrawal speeds and/or fine yarn numbers.
British Patent Specification No. 1,393,663 relates to an open-end rotor spinning machine and a device for measuring the count and twist factor of the material being spun. Although this arrangement utilizes the detection of the number of revolutions of a spinning rotor and the sliver feed and yarn withdrawal speeds to determine yarn twist in a rotor spinner, these are also indirect measurements of yarn twist. Because of the different operations of the yarn turning friction surface in rotor spinners and open-end friction spinning machines using friction rollers or the like, such indirect measurements of the twist would not work with precision friction spinning machines of the type contemplated by the present invention.
One object of the invention is to provide a method of permitting a precise quality control of the spun yarn and to accommodate a correspondingly slight change or adjustment of at least one parameter of the spinning conditions.
This object is achieved according to the invention by detecting the yarn twist of the yarn produced at the spinning units and monitoring the same by means of a measuring and evaluating device.
An important criteria for the quality check of the yarn is thereby the ability to monitor the yarn twist according to preferred embodiments of the present invention. It is also contemplated to additionally test for yarn uniformity and/or yarn stability in certain preferred embodiments of the invention. The detection of yarn twist is important because it facilitates immediate signaling of any deviations in the friction effect of the friction zone of the respective spinning unit so that measures can be directly taken to eliminate any fluctuations in the friction effect.
In certain advantageous preferred embodiments of the invention, it is provided to monitor the yarn twist of a running yarn produced in the spinning units. This monitoring function can be conducted by either a yarn testing device arranged at each spinning unit, or by a servicing apparatus equipped with such type of yarn testing device which is periodically assigned to all spinning units according to certain embodiments of the invention. The first embodiments offer the advantage of a continuous monitoring, while the second embodiments advantageously keep operational expenditures to a minimum.
In a further development of preferred embodiments of the invention, it is provided to insert the yarn being monitored at a spinning unit into a movable servicing apparatus and to feed the same to a measuring device. This development takes into account that it becomes increasingly difficult to monitor the yarn twist in a yarn running with high production speeds. However, if the yarn is inserted into a movable servicing apparatus, its yarn twist can then be measured accordingly while the same runs very slowly or stands still all together. The arrangements necessary for this procedure need only be provided once per spinning machine, thereby keeping the operational costs in bearable limits.
In a further development of certain preferred embodiments of the invention, it is provided to continue the operation of the spinning unit during measurement. The yarn running through the servicing apparatus and produced during this measurement is returned to the spinning unit upon completion of the task and is wound upon a take-up spool of same. In these embodiments, the measuring of the yarn twist and the required adjusting of the spinning unit are accomplished without interrupting the yarn production of the respective spinning unit. These arrangements require a storage device to be provided in the servicing apparatus which safely accommodates the yarn continually produced during the measurement, and which allows subsequent withdrawal of the yarn out of the storage device.
In another embodiment of the invention, it is provided to discontinue the operation of the spinning unit upon insertion of the yarn into the servicing apparatus, and upon the removal of a yarn test sample, to peform a piecing operation at the spinning unit. Because a servicing apparatus capable of performing a piecing process is generally contemplated for commercial friction spinning machines, this method can be accomplished relatively inexpensively.
In another development of preferred embodiments of the invention, it is provided to obtain a yarn test sample for measuring the yarn twist from a take-up spool of a non-operating spinning unit. This would further reduce the expense for any necessary equipment for removing a yarn sample, because a servicing apparatus can at least in part be utilized also which is commonly used for performing a piecing process. In this embodiment, it is also advantageous to remove a yarn sample from the take-up spool during a piercing process at this spinning unit. Then, in one working step, this servicing apparatus can accomplish not only the piecing, but also the measurement of the yarn twist, and additionally, as the need arises, attend to the adjustments of one or serveral parameters of the spinning conditions which are determined to be desired based on the measurement of the yarn twist.
In a further development of preferred embodiments of the invnetion, it is provided that the servicing apparatus establishes conditions at a particular spinning unit during the testing of the yarn twist prior to changing any parameters of the the actual value of one or several parameters of the spinning conditions thereof, and utilizes this actual value in the measuring and evaluating device. The possibility is thereby created to have the measuring and evaluating device determine which of the parameters are best to be adjusted for obtaining the desired results.
In a further development of preferred embodiments of the invention, it is provided that the measuring and evaluating device of the servicing apparatus compare the measured actual value to the preset limiting values of the parameters of the spinning conditions with regard to any necessary adjustments based upon the measured yarn twist. Further, the measuring and evaluating device discontinues operation of the spinning unit when values exceed the limiting values and/or marks the spinning unit that requires service. Prior to restarting the spinning unit and continuing of yarn production, the necessary service tasks are performed such as a cleaning process or treating or processing the surfaces of the friction zone at this spinning unit. These servicing tasks put the servicing apparatus into a position to meet the required spinning conditions.
In a further development of preferred embodiments of the invention, it is provided that the measuring and evaluating device of the servicing apparatus compares the measured actual value of the parameters of the spinning conditions with the preset limiting values of the parameters, in consideration of the necessary changes based upon the measured yarn twist. In addition, certain preferred embodiments include devices for assigning means for cleaning and/or post-treatment, especially of the friction zone, to the respective spinning unit requiring adjustment after having exceeded the limiting values. This part of the maintenance of the spinning unit is thereby also fully automated.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings, which show for purposes of illustration only, several embodiments constructed in accordance with the present invention.